1. Field of the Invention
In the art relating to. fluid couplings for pipe or tubing, the so-called plumbing "union" has been employed for many years. Ordinarily two mating parts of a union are drawn together in a fluid-tight manner by rotating an internally threaded coupling member captive with respect to one pipe or tubing member over a correspondingly externally threaded ferrule attached to another pipe or tubing member. Usually this operation requires two-handed operation and the use of a wrench requiring substantial clearances about the coupling. Such limitations are serious obstacles where the connection of fluid lines must be accomplished by an astronaut in space, assembling a space station, for example.
The size of a space station active thermal control system precludes ground assembly of all piping unions and as many as 50 to 250 fluid connections must be assembled in orbit by Astronauts outside of their pressurized space vehicle in the performance of extravehicular activity (EVA), and/or telerobotic devices. Fluid lines in that application may range in size from approximately 1 centimeter to 7 centimeters in diameter and, particularly the larger sizes require large torques for proper assembly.
The field of the invention may be summarized as automated pipe segment assembly systems employing plumbing unions, particularly in space stations where conventional assembly techniques are unacceptably burdensome for the EVA astronauts required to perform the task.
2. Background Art
Power wrenches for various applications have been developed in the mechanical arts and are described in the patent literature. Pertinent background patents known to the originators of the present invention comprise U.S. Pat. Nos. 2,795,985; 2,907,242; 2,952,177; 3,290,063; 3,239,245 and 3,668,949.
U.S. Pat. No. 2,795,985 discloses a plumbing joint of the spigot and socket joint type. A resilient compressed as a threaded head member is rotated in communication with socket member threads to compress a resilient gasket forming a seal. The head member has a gear toothed periphery which acts as a ring gear. A pinion gear on a shaft engages this ring gear. Rotation of the shaft by means of a wrench or the like provides substantial mechanical advantage but, in the space station environment, offers no assembly advantage. In fact, its operation would be quite burdensome for an astronaut in that critical hand tool alignment would be required.
In U.S. Pat. No. 2,907,242 a plumbing union type of pipe coupling is shown. An annular gear is engaged by a pinion gear on a shaft extending normally with respect to the coupled pipe. The orientation of this shaft provides more convenient tool interface where a plurality of pipe joints may be in lateral juxtaposition, as in a duct or trough, but in the space station application the use of this device would be burdensome to the astronaut assembling a piping system in space.
U.S. Pat. No. 2,952,177 discloses a power wrench apparatus for operating a chuck or the like and as such has only very limited relevance to the novel combination of the present invention.
U.S. Pat. No. 3,290,063 describes a power-operated pipe coupling including a rack and pinion gearing arrangement for applying compression between interfaced pipe segment ends, but does not afford relief from tool alignment and operation inconvenience.
U S. Pat. No. 3,239,245 employs a plumbing union with a gear toothed periphery on its rotatable member. A worm gear on a shaft tangential to the rotatable member periphery provides mechanical advantage, but does nothing to enhance tool alignment or operator ease.
The concept of a power wrench for operating the rotatable member of a pipe coupling device is shown in U.S. Pat. No. 3,668,949, particularly in an underwater situation. Required positioning of the power wrench in respect to a shaft is not sufficiently convenient to be applicable to the space station environment. The disclosure of U.S. Pat. No. 3,668,949 contemplates a power wrench device having an output worm gear. Means are provided for positioning this worm gear to drive a spur gear mounted on a shaft. Rotation of this shaft effects rotation of undisclosed elements pertinent to underwater pipe connection. That combination is said to apply particularly to oil and gas wellhead connections under water. The structure would not be sufficiently convenient for the space station application. None of the prior art references show the particularly advantageous device of the present invention and no combination of the references could produce the device of the present invention by exercise of ordinary skill.